The invention relates to an indicator apparatus having a ring pointer which is in the form of a ring or annular segment and is mounted so that it can move in the circumferentially. The indicator apparatus includes a drive unit which drives the ring pointer circumferentially, where the ring pointer has a stop face, and the indicator apparatus has a stop which interacts with the stop face so as to limit the circumferential movement of the ring pointer.
In the age of ever increasing information density in the cockpit of a motor vehicle, in particular manufacturers of combination instruments are faced with the difficult task of presenting a high density of information with, in some cases, safety related significance in a way which can be perceived satisfactorily. At the same times, it is also necessary to comply with relevant safety regulations which are intended to ensure a certain degree of precision, for example of the speed indicator, together with sufficient fail safety measures. In addition, this complex function must be provided with an attractive design, which frequently places strict limits on functionality and has a decisive influence on the requirements made of the overall structure.
In the compression of information, what are referred to as ring pointer, such as are described, for example, in EP 0 997 338, have proven expedient since these indicator devices do not require a central pointer axle. As a result, an analog indication in the classic sense is permitted, while at the same time leaving the central region of the indicator field free of the device's own components for a multifunction displays. Such a multifunction display may be composed, for example, of various small displays or of a relatively large graphic-compatible display.
Compared to conventional indicators with central indicator axes, the driving of the ring pointer, its bearing and its synchronization for a precise indication are much more complex. The usually circular ring pointer must be relatively dimensionally stable, despite its usually filigree embodiment so that it does not deform too much under the force of the drive. In addition, the ring pointer has to be mounted at a plurality of points over its circumference, and in this context the arrangement of three radial bearings over the circumference has proven expedient.
So that, for example, a speed indicator satisfies the high indication precision, a high power drive unit is provided which, for example in the case of severe braking, gives the ring pointer sufficient acceleration. In this context, the high tangential forces on the ring pointer can bring about an undesired radial offset, which not only adversely affects the indication precision for the moment of the offset but also desynchronizes the pointer. In the worst case, the drive unit is permanently no longer in engagement with the ring pointer because of the displacement of the ring pointer. In order to prevent this, previous embodiments have proposed radial stops which limit the possible radial offset of the ring pointer. However, fabricating these stops in a way which corresponds to the geometry of the filigree ring pointer requires extremely high fabrication precision, as a result of which considerable costs are incurred.